PC/104 is a de facto standard (IEEE P996.1 standard for Compact Embedded-PCModules) which has a compact form-factor (size 3.6 by 3.8 inches) and a unique self-stacking bus which eliminates the cost and bulk of back planes and card cages. The PC/104 cards use pin-and-socket connectors that are rugged and reliable. The electrical bus is a relaxed bus drive (6 mA) which lowers power consumption (to 1-2 Watts per module) and minimizes component count.
FIG. 1 depicts a module stack of PC/104 cards. The distance between cards 10a-d is precisely controlled by the use of spacers 12. The details of the connector are depicted in detail in FIGS. 2A and B. In FIGS. 2A and B, stackthrough cards use passthrough connectors having male and female parts. A female connector assembly 16 is included on each card 10.
Conventional electrical connector assemblies include complementary male and female connectors for establishing electrical connections between electrical systems and components. The standard PC/104 connectors on a designated card are designed to supply signals to components on the designated card and also to pass signals between cards stacked below the designated card and cards stacked above the designated card.
The pins of the PC/104 connectors are assigned to signals of the ISA bus. Thus, all signals generated by components on a PC/104 card that are transmitted via pins on the PC/104 connector must comply with the ISA specification for the signal carried by that pin.
The PC/104 standard has been extended by the PC/104-Plus standard which incorporates all the features of PC/104 but also includes an additional connector that supports the PCI bus. In the following, for convenience, reference-to PC/104 is to be understood to include reference to the PC/104-Plus.
Referring to FIGS. 2A and B, to accomplish the pass-through function, the connectors include a female connector assembly 16 having an array of pin slots 18 formed therein. The pins 28 include an elongated male connector portion 30, a head 31, and a female connector portion 32. There are various pin configurations used in the industry. In one type of connector, the female connector portion 32 is in the form of a clip attached to the head of the pin. The clip can include tabs 33 that recess into a notch formed in the pin slot. When the pin is inserted into the slot the tab engages the notch to precisely control the depth of insertion of the pin into the bottom of the pin slot 18. The female connector assembly 16 is mounted on the major surface of a first card 10a. A first set of pins 34 have their heads inserted into the female connector assembly 16 mounted on the first card 10a and pass through plated holes in the card which are connected to electrical traces on the card that transmit signals to components on the card.
A second set of pins 36 are inserted into the female connector assembly 16 of a second card 10b stacked above the first card. The spacers 12 for stacking the cards, the length of the pins, and the precisely controlled insertion depth of the female connectors are designed so that the male connector portions 30 of the second set of pins 36 are aligned with pin slots and so that the ends of the male connector portions 30 of the second set of pins 36 are inserted a precise distance into the pin slot and engage the female connector portions 32 of the first set of pins 34 to establish an electrical connection to conduct the signals to the components on the second card.
Companies embedding PC technology, having applications where space is limiting, can now benefit from a standardized system architecture complete with a wide range of multi-vendor support. For PC/104 modules that require I/O interconnect of signals not defined for PC/104 or PC/104-Plus connector buses various techniques are utilized.
One technique is to use custom I/O connectors that are typically designed by vendors to interconnect I/O signals between modules from the same vendors. Depending on the number of interconnecting I/O signals required and the density of each board, the I/O custom connectors can quickly become an a problem because board space is valuable in a compact architecture design.
Another technique is to transform the non-standard signal to a bus signal, transmits the converted signal to the next card using the connector, and then transform the bus signal back to the not-standard signal. The problem with this technique is that extra components for transforming the signals are required which adds to the complexity and cost of the system.
According to one aspect of the invention, these problems are solved by re-using the PC/104 connector pins for non-bus I/O signals between modules without interfering with the PC/104 electrical bus specifications.
According to another aspect of the invention, for certain PC/104 modules designs that do not necessarily use the entire pin count on the PC/104 connector, the unused pins on the PC/104 are used to route required extra I/O signals in between these modules.
According to another aspect of the invention, in order not to interfere with PC/104 electrical connecting bus, these identified pins that are design specific, can be made to connect the two or more modules together, while keeping electrical isolation from the originally designated pins stated by the PC/104 spec.
According to another aspect of the invention, one of the modules is the xe2x80x9cbottom modulexe2x80x9d i.e. non-stacking, while the next module stacked above it, is the module to which the I/O signals need to route to. To isolate the I/O signals from the main PC/104 bus, the upper module connector provides the isolation. The isolation mechanism is achieved by recessing the metal connector within the pins socket, and partially plugging the hole itself This mechanism eliminates any interference with the PC/104 bus stack up modules, while allowing unused pins to be used for routing channels within the PC/104 connector.
Other features and advantages of the invention will be apparent in view of the following detailed description and appended figures.